The investigation will determine the interrelationship of neurons and functionally related groups of neurons at the margin of an experimental epileptogenic focus induced by penicillin. The physiological properties of individual neurons in primary visual cortex will be studied before and after penicillin application. Cortex at the margins of the epileptogenic focus will be explored to determine the degree and character of neuronal involvement. The units will be defined as to their receptive field orientation specificity, the receptive field location with respect to the activation field and ocular dominance. The data so obtained will determine to what degree physiologically related groups of neurons continue to act as a unit during epileptogenesis. Such data will provide information regarding some mechanisms of the neural aggregate response in epileptogenesis and perhaps indicate an elementary unit of epileptogenesis.